FIGS. 1 and 2 show typical, prior art planer side heads for use in commercial manufacturing of construction lumber and finished wood products. Such heads can generically be referred to as “cutting heads” because they produce cuts in the workpiece. They include, typically, a plurality of knives and are connected, typically by a drive-shaft, to a motor or engine that rotates the cutting head about an axis of rotation.
FIG. 1 shows a planer side head 10 known as an “L” type, and FIG. 2 shows a planer side head 20 known as an “LV” type. FIG. 3 shows for greater clarity wedging elements 24 (24a, 24b) that form part of a wedging bolt assembly for clamping a knife in the head 20. While persons of ordinary skill are, by definition, familiar with L and LV planer side heads, a brief description of some salient features of these heads is provided here for general understanding, and focus.
A planer side head has an essentially disc-shaped or cylindrical body 11, and is caused to rotate about a cylindrical axis of rotation of the head “R.” Extending into the body are a plurality of axially extending pockets 25 that are uniformly and azimuthally spaced-apart along the circumference of the body as shown. These pockets are adapted to receive corresponding knives 27 (27a in FIGS. 1 and 27b in FIG. 2) that project cutting edges 35 outwardly from the pockets.
Each pocket 25 has a back surface 26 for receiving the knives 27. As it appears in the end view of FIG. 4 (corresponding to the L-type head of FIG. 1), this back surface is congruent with a line “L1” that joins the circumference of the body 11 at a point “P1.” This line L1 is aligned closely, i.e., to an angle θ1 that is within 5 degrees from another line “L2” drawn through the same point P1 and the axis of rotation R. This geometry is characteristic of an L or LV-type planer side head, and is for purposes herein considered to be a distinguishing characteristic with respect to other types of cutting apparatus.
FIGS. 5 and 6 show a knife 27a for use in the L-type planer side head of FIG. 1, and FIGS. 7 and 8 show a knife 27b for use in the LV-type head. As can be seen, the knives 27a and 27b vary only with respect to their adaptations for being mounted in the pockets and are otherwise essentially identical.
Referring to FIG. 9, each of the knives 27 has a cutting end 40 that projects at an angle from a shank end 42 that is received in a pocket, giving the knife an approximate “L” shaped configuration. The shank end 42 has a back surface 43 that is received by the back surface 26 of the pocket in which the knife is installed. As can be seen particularly in FIGS. 6 and 8, the back surface 43 of the shank 42 has a series of axially disposed corrugations 41 that mate with corresponding corrugations 45 in the back surface 26 of the pocket (FIGS. 1 and 2). These corrugations are provided for incrementally adjusting the radial position of the cutting edge 35 of each knife 27, as discussed below.
Referring to FIG. 10, the cutting end 40 has a cutting edge 35 that includes a face-cutting edge portion 37 disposed between two corner-cutting edge portions 39 (39a, 39b). Each knife 27, when mounted into the planer side head and rotated, produces a cut in an article of wood 8 (or other material) having the profile “PR.”
To produce a planer face-cut “Fs,” the face-cutting edge portion of the cutting edge 35 is linear, and to produce the two arcuate corner cuts “r,” the corner-cutting edge portions of the cutting edge 35 are preferably circular arcs, for producing radius cuts, although other curvatures could be provided in one or both of the corner-cutting edge portions to produce any desired arcuate corner cuts.
The cutting edge 35 is a line or edge of joinder of a planar front side surface 44 (see FIGS. 5 and 7) of the cutting end 40, facing the direction of rotation of the side head, and a back side surface 46 of the knife (see FIGS. 6 and 8). Referring to FIG. 11 (corresponding to the L-type head of FIG. 1), the front side surface 44 (shown in edge view) defines a cutting angle θC with a line intersecting an outermost tip 46 of the knife and the axis of rotation R. This cutting angle is an important process parameter, and in both the L and LV-type planer side heads it has a standard, industry accepted value which is assumed for descriptive purposes herein to be 25+10/−20 degrees.
A grinder is used to grind the front side surface 44 of a knife 27 to refresh or recondition the knife, but this causes the cutting edge 35 to recede in both azimuthal and radial directions, changing primarily the cutting diameter of the planer head, but also changing secondarily the cutting angle. However, the recessions in both directions are found to be satisfactorily compensated for by moving the knife outwardly along the aforementioned line L1 (FIG. 4) in increments defined by the aforementioned corrugations.
The shank end 42 of the knives 27 provide the necessary adaptation for mounting the knife in the particular type of planer side head. Referring to FIGS. 1 and 6, the shank end 42 of the knife 27a for use in the L-type side planer head includes a, typically, planar front surface 37. Toe bolts 41 are threadably received in the body 11 so that ends 14 of the bolts extend into the associated pockets 25 by adjustable amounts. The ends 14 make contact with the front surface 37 and, by tightening the bolts, the knife 27a is clamped firmly in place.
Referring to FIGS. 2 and 8, in the LV-type planer side head, a more dense knife spacing is provided by the use of axially extending wedge bolts 22 used to draw together wedge elements 24 (24a, 24b) against axially opposed, relatively inclined sides 38 of a knife 27b. Tightening the axially extending wedge bolts wedges the knife firmly in place.
Aside from the differences in how the knives 27 are adapted for being clamped in the pockets, the L and LV type planer side heads are essentially identical for purposes herein.